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- 1 Can you please tell me about natural, conservative treatments for a retronychia toenail that don't involve getting it removed.
- 2 what is a healthy level of Vitamin B12 to have to avoid illness.
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what is a healthy level of Vitamin B12 to have to avoid illness.
The short version: a single serum B12 number is a weak guide; the functional markers tell you more, and the "healthy" threshold depends on who you are.
The retrieved studies show that serum B12 alone misses a lot. In one case, a man with neurological symptoms had a serum B12 of 254 pg/mL, which many labs call normal, yet his methylmalonic acid (MMA) was massively elevated at 36,000 nmol/L, and he had brain changes on MRI that reversed with B12 therapy [4]. Another case showed functional deficiency despite a serum B12 above 2,000 pg/mL from self-supplementation, because nitrous oxide had blocked B12 from working [7]. So the serum number can be falsely reassuring in both directions.
The better markers are MMA and homocysteine. In 434 episodes of confirmed B12 deficiency, MMA was elevated in 427 and homocysteine in 416 [6]. In a study of neurological patients, those with low serum B12 had higher MMA in both blood and spinal fluid than controls [5]. But these markers have their own trap: in the elderly, kidney function strongly influences both MMA and homocysteine, so a high MMA can mean poor kidneys rather than B12 deficiency [8].
What level to aim for? One study of healthy Italian blood donors found only about 25 in 100 had serum B12 above 350 pmol/L, a threshold often used for adequacy [9]. In children with deficiency, oral treatment raised mean B12 from 182 to 482 pg/mL at one month, and that was enough to improve hemoglobin in anemic kids [1]. The evidence here does not define one universal "healthy" number, because the right level depends on your kidneys, your genes, and whether you take drugs like metformin or acid blockers that deplete B12 [2][3][10].
My call: do not chase a single serum number. If you are symptomatic or at risk, test MMA and homocysteine alongside B12, and treat the person, not the lab value. Confidence: moderate.
Sources used 10
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The Efficacy of Oral Vitamin B12 Replacement for Nutritional Vitamin B12 Deficiency
In a prospective cohort of 79 children aged 6 months to 18 years with nutritional vitamin B12 deficiency (serum <300 pg/mL), oral cyanocobalamin significantly increased mean vitamin B12 levels from 182 ± 47.6 to 482 ± 318 pg/mL at 1 month (P=0.001) and to 384 ± 167 pg/mL at 3 mo…
DOI: 10.1097/mph.0000000000001037 -
Effects of proton pump inhibitors on vitamin B12
A concise review of evidence linking long-term proton pump inhibitor (PPI) use to vitamin B12 deficiency in older adults, summarizing proposed mechanisms, clinical implications, and recommendations for monitoring and management.
DOI: 10.1016/j.maturitas.2014.06.005 -
Effect of Vitamin B12 supplementation on the Diabetic Peripheral Neuropathy- a Review
This narrative review concludes that long-term metformin use is linked to vitamin B12 deficiency, elevated methylmalonic acid, and a higher occurrence of diabetic neuropathy, while B12 supplementation may be beneficial and is reported without adverse effects.
DOI: 10.32350/ihr.21.05 -
Vitamin B 12 Deficiency With Bilateral Globus Pallidus Abnormalities
This case report describes a 43-year-old man with vitamin B12 deficiency presenting with extrapyramidal symptoms and reversible bilateral globus pallidus abnormalities on MRI, associated with elevated methylmalonic acid and homocysteine, autoimmune gastritis, and full clinical/r…
DOI: 10.1001/archneurol.2011.1084 -
Cerebrospinal fluid methylmalonic acid concentrations in neurological patients with low and normal serum cobalamin concentrations
This study investigates the concentrations of methylmalonic acid (MMA) in cerebrospinal fluid (CSF) and serum of neurological patients with low serum cobalamin levels, finding significantly elevated MMA levels in patients compared to controls, suggesting cobalamin deficiency in …
DOI: 10.1111/j.1600-0404.1998.tb05976.x -
Sensitivity of serum methylmalonic acid and total homocysteine determinations for diagnosing cobalamin and folate deficiencies
This study evaluates the sensitivity of serum methylmalonic acid and total homocysteine levels in diagnosing cobalamin (vitamin B12) and folate deficiencies, demonstrating their high diagnostic accuracy compared to traditional serum cobalamin measurements.
DOI: 10.1016/0002-9343(94)90149-x -
Chronic Nitrous Oxide Toxicity Despite Elevated Serum Vitamin B12 Level
A 28-year-old male developed chronic nitrous oxide neurotoxicity with persistent paresthesias despite elevated serum vitamin B12 (>2000 pg/mL) from prophylactic self-supplementation, demonstrating functional B12 deficiency can occur despite supratherapeutic serum levels.
DOI: 10.5811/cpcem.39674 -
Glomerular filtration rate as measured by serum cystatin C is an important determinant of plasma homocysteine and serum methylmalonic acid in the elderly
This study investigates the relationship between glomerular filtration rate (GFR) as measured by serum cystatin C and the levels of plasma total homocysteine and serum methylmalonic acid in an elderly population, revealing that GFR significantly influences the prevalence of elev…
DOI: 10.1111/j.1365-2796.2006.01732.x -
B vitamin blood concentrations and one-carbon metabolism polymorphisms in a sample of Italian women and men attending a unit of transfusion medicine: a cross-sectional study
A cross-sectional study of healthy Italian blood donors (18–65 years) quantified plasma folate, vitamin B12, vitamin B6, and homocysteine along with four one‑carbon metabolism gene polymorphisms, finding limited adequacy of folate/B12 in many subjects and a gene–nutrient interac…
DOI: 10.1007/s00394-020-02448-1 -
Association of Biochemical B12 Deficiency With Metformin Therapy and Vitamin B12 Supplements
This study investigates the prevalence of biochemical B12 deficiency among U.S. adults aged 50 and older with type 2 diabetes on metformin compared to those not on metformin and those without diabetes, revealing a higher deficiency rate in metformin users and questioning the ade…
DOI: 10.2337/dc11-1582